The discovery of a new virus, HBLV, was published in "Isolation of a New Virus, HBLV, in Patients with Lymphoproliferative Disorders" Salahuddin et al. Science Vol. 234, p. 596 (Oct. 31, 1986). A companion article, "Genomic Analysis of the Human B-Lymphotropic Virus (HBLV)" Josephs et al., id. at 601, provided additional evidence that HBLV is a novel human Herpesvirus.
The connection between HBLV and human disease is not firmly established. HBLV may have a role in some lympho-proliferative and immune system disorders, particularly autoimmune disease conditions. It may be responsible for some rare forms of human cancer such as B-cell lymphomas. HBLV may be associated with chronic mononucleosis-like syndrome, as suggested by "Mystery Disease at Lake Tahoe Challenges Virologists and Clinicians" Barnes, id. at 541.
The HBLV primarily infects human B lymphocytes, which are part of the human white-cell immune system. In the past, the HBLV virus was obtained through culture of freshly-isolated human B lymphocytes from adult peripheral blood, bone-marrow or spleen cells or from freshly isolated phytohemagglutinin-stimulated human lymphocytes from umbilical cord blood.
The virus destroys the cells it infects in vitro. This characteristic presented an obstacle to further study of the virus and to production of a sufficient quantity of the virus for use in biochemical characterizations and diagnostic tests. Only a small amount of HBLV could be grown in tissue culture before cell destruction terminated the viral production process.
With the exception of the umbilical cord blood lymphocytes, B-lymphocytes from other human sources are frequently infected with the Epstein-Barr virus, another member of the Herpesvirus family. This coinfection makes B-lymphocytes from the adult sources less-desirable target cells for production of HBLV.
Therefore, only fresh human umbilical cord lymphocytes were used for the cultivation of HBLV. Human umbilical cord lymphocyte availability is limited, preparation for tissue culture production is complicated and the yield of lymphocytes per cord is typically low and extremely variable. Furthermore, cords must be collected and processed within 24 hours. For example, using the cord blood procedure for tissue culture production of HBLV, a typical human umbilical cord yielded 10 ml of cord blood with 1.times.10.sup.6 lymphocytes per ml. This amount of lymphocytes yielded about 10-20 ml of supernatant culture fluid containing HBLV at a concentration of about 10.sup.7 virus particles per ml after 7 days in tissue culture. Total yield of virus was 1-2.times.10.sup.8 particles per cord blood donor. The cord blood procedure is an impractical method for production of other than tiny quantities of HBLV for some research purposes, and is difficult or impossible to scale-up.